1. Field of the Invention
The present invention relates to a cassette tape driving device which can drive capstans, reel bases and a head base by using a single motor.
The present invention relates also to a cassette tape driving device which can assuredly change operation modes from one to another.
2. Description of the Related Art
A cassette tape driving device rotates a capstan and reel rotary shafts, brings a magnetic head into contact with, or separates the magnetic head from, a magnetic tape, and drives a head base in order to bring a pinch roller into contact with, or to separate the pinch roller from, the capstan. A conventional cassette tape driving device drives the capstan and the reel rotary shafts by means of a single motor, and drives the head base through the use of a single solenoid. In this structure, however, the motor and the solenoid are required, the number of parts is large, and the mechanism is complicated, entailing the problem that the cost of manufacturing the device is high.
In order to solve such a problem, Examined Japanese Utility Model Application No. 7-9214 discloses a cassette tape driving device which drives the capstan, the reel bases and the head base by means of a single motor.
The cassette tape driving device disclosed by Examined Japanese Utility Model Application No. 7-9214 has the structure illustrated in FIG. 17. Using a motor 50, the above-mentioned cassette tape driving device drives a capstan 70, reel gears 160 and 170 coupled to the rotary shafts (reel bases) for rotating a tape-up reel and a supply reel, and a head base 210 to which a magnetic head 100 is fixed.
The basic operation of the above cassette tape driving device will now be described with reference to FIG. 17.
In the case of playing back the information recorded on a cassette tape or recording information on the cassette tape, the motor 50 is rotated in the direction of an arrow YC. This rotation is transmitted to a pulley 120 through a belt 60. A central gear 130 is fixed to the center of the pulley 120, and one end of an arm 140 is rotatably attached to the central gear 130. A planetary gear 150 revolves around the central gear 130 in the state of being in mesh with the central gear 130. A mode changing gear 180 is provided in the orbit along which the planetary gear 150 revolves.
When the central gear 130 rotates in the direction of the arrow YC, the planetary gear 150 revolves around the central gear 130 in the direction of the arrow YC in accordance with the rotation of the central gear 130. The planetary gear 150 revolves until its teeth 155 engage with the teeth 185 of the mode changing gear 180. When the teeth 155 engage with the teeth 185, the planetary gear 150 halts and transmits the rotation of the central gear 130 to the mode changing gear 180.
The mode changing gear 180 is provided with switching cams 190 and 200. The switching cams 190 and 200 rotate in accordance with the rotation of the mode changing gear 180. The head base 210 has a bent piece 215, and is urged by a spring 220 in the direction of an arrow YB. While rotating, the switching cams 190 and 200 press the bent piece 215. The head base 210, the bent piece 215 of which is being pressed by the switching cams 190 and 200, moves in the direction of an arrow YA against the urging force exerted by the spring 220. The magnetic head 100 provided on the head base 210 also moves in accordance with the movement of the head base 210, and comes into contact with the magnetic tape of the cassette arranged on reel bases 160 and 170. Further, the planetary gear 150 and that circumferential part of the mode changing gear 180 which does not have the teeth 185 become face to face with each other, the mode changing gear 180 and the planetary gear 150 disengage from each other, and the mode changing gear 180 halts. Accordingly, the magnetic head 100 and the magnetic tape keep contacting each other.
In the case of stopping the cassette tape driving device, the motor 50 is rotated in the direction opposite to that of the arrow YC. Upon this reverse rotation, the planetary gear 150 revolves in the direction opposite to that of the arrow YC, comes into mesh with the mode changing gear 180, and rotates the mode changing gear 180 in the direction opposite to that of the arrow YC such that the bent piece 215 and the cam 190 or 200 disengage from each other. Due to the urging force, the head base 210 returns to its original position, and the magnetic head 100 separates from the magnetic tape.
The planetary gear 150 needs to assuredly transmit the rotation of the central gear 130 to the mode changing gear 180 with the planetary gear 150 being in mesh with the central gear 130 and the mode changing gear 180. However, there is the case where the engagement between the teeth 155 of the planetary gear 150 and the teeth 185 of the mode changing gear 180 is not satisfactory because of a manufacturing error or the like. In such a case, the planetary gear 150 does not stop revolving and cannot transmit the driving force of the central gear 130 to the mode changing gear 180. Also in the case where the load on the planetary gear 150 is heavy, the planetary gear 150 cannot stop revolving and cannot transmit the driving force of the central gear 130 to the mode changing gear 180.
Some cassette tape driving devices are an auto-reverse type. The auto-reverse type cassette tape driving device disclosed in Examined Japanese Utility Model Application 7-9214 has two magnetic heads, and uses one of them in accordance with the direction in which the magnetic tape travels. However, the mechanism of this cassette tape driving device is complicated owing to the presence of the two magnetic heads, and the cost of manufacturing the device is high.
Some auto-reverse type cassette tape driving devices have a structure for turning one magnetic head in accordance with the tape traveling direction. However, this type of cassette tape driving device requires a solenoid for turning the magnetic head by 180.degree., the number of parts is large, and the mechanism is complicated, which entails the problem that the cost of manufacturing the device is high.
The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide an auto-reverse type cassette tape driving device which can perform the basic operation with a single motor.
It is another object of the present invention to provide a cassette tape driving device which can assuredly transmit the rotation of the central gear to the mode changing gear.